Project Summary This proposal aims to determine the contribution of T cells to pathology in an alpha-synuclein (?-syn) based mouse model of Parkinson disease (PD). Our lab has pursued the idea that ?-syn, an intracellular protein abnormally aggregated in PD brains, is a trigger for the innate immune and adaptive immune system activation associated with PD. Targeted overexpression of ?-syn in the substantia nigra of mice driven by an adeno-associated virus vector (AAV2-SYN) recapitulates the microgliosis, T cell infiltration, and slow progressive cell death observed in human PD. Additionally, knocking out antigen processing machinery (MHCII) reduces ?-syn induced inflammation and neurodegeneration, suggesting a possible T cell mediated disease mechanism. The proposed research attempts to build upon these findings, by investigating the hypothesis that activation of T cells is required for mediating the dopaminergic neurotoxicity of alpha-synuclein in vivo. First, proposed experiments will determine whether alpha synuclein can lead to T cell activation in an AAV2-SYN mouse model of PD. Changes in brain effector T cell populations will be measured through IHC and flow cytometry in BL6 mice injected with AAV2-SYN or a control AAV2 vector (AAV2-GFP) at 2, 4, and 12 weeks post-injection. Next, experiments to determine the effect of T cells on myeloid activation in response to ?-syn will be conducted. Changes in activated myeloid populations will be measured in AAV2-SYN treated BL6 and mice lacking CD4 T cells (either by genetic KO or pharmacological treatment) by IHC and flow cytometry 2, 4, and 12 weeks post injection. Lastly, the hypothesis that blocking T cells (either by genetic KO or pharmacological treatment) into the CNS will reduce the neurodegeneration associated with ?-syn overexpression will be tested. Both control BL6 mice and mice with a deficiency in CD4 T cells will be injected with AAV2-GFP and AAV2-SYN in the substantia nigra. Dopaminergic neuron loss will be assessed at 6 months post-injection with unbiased stereology. Collectively, the completion of these experiments will aid in the development of new therapeutics targeting T cells that work to prevent neuroinflammation as a neuroprotective treatment for Parkinson disease. The proposed training plan is sponsored by Dr. David Standaert and Dr. Ashley Harms. The overall goal of the training plan is to provide the PI with a solid foundation for a successful career as a research scientist studying neuroimmunology. Included in the training plan are experiences that help the PI: 1) gain competence in a variety of techniques integrating neurobiology and immunology, 2) collaborate with other scientists, 3) develop hypothesis-driven research, 4) present data in a written and oral format, 5) effectively integrate research with clinic, and 6) responsibly conduct research.